The Bears have tabbed Mel Tucker to become the team's defensive coordinator, according to three league sources.
The Bears are expected to formally announce the hire Friday evening.
Tucker had been the Jacksonville Jaguars defensive coordinator since 2009. Although the Jaguars unit was terrible last season, the defense was ranked 6th overall in 2011. Tucker has extensive college and pro coaching experience. 
Tucker has run both 4-3 and 3-4 defenses, and he's worked with the likes of Jack Del Rio and Nick Saban.
He served as the Jags interim head coach after Del Rio was fired, and he's interviewed for a handful of head coaching vacancies.
Former Bears and Jaguars safety Chris Harris called him an "outstanding coach."
Asked why, Harris said, "He's a guy that understands how teams are trying to attack him.
"He believes in his system and doesn't panic when things aren't going to plan."
The hire is a significant one since Tucker will essentially run the defense because new head coach Marc Trestman has an extensive offensive background.
As long as he is willing to run a Tampa 2
I was sorry that Marinelli decided to leave. Focussing on him was one of Lovie Smith's smartest moves. That his offensive coordinater picks were so bad is the reason he is gone.. Batter choices there and he might still be the Bears' coach.
I'm sorry to see that the Trestman chose a defensive coordinator because he knows Lovie Smith's defense. I was really hoping that they'd switch to a more aggressive system.
I understand that the Bears want to utilize the defensive players they have now, because they have some very good ones. But the best defensive players are all old and won't be around much longer. Urlacher is already shot, for example. I think the Bears would be better off rebuilding the defense with a better, more aggressive style with bigger defensive linemen. Keeping this style just to utilize the good players they have now might come back to bite them in a few years.
Hey Wrigley:
Hope you are doing well and still found on football Sunday at Rickey's?
As for the new D Coordinator, I always am a little perplexed when wholesale changes are made with the defense, particularly this years D that in my opinion played so well.
My hope is that the new Bears defensive schemes are further bolstered by top cover corners and safeties to allow for the creative blitzes and pressure that creates fast and fierce pressure on the Qb's.
Bears D has a historical standard, reputation and Bear history it must live up to or true Bear fans will rebel. NFL teams need to know again, (even if the Bears lost) that the Bears are the most physical and nasty team in the league so that hey will dread having he Bears on the schedule, from the physical whipping they will receive in Chicago or any city they play.
The Chicago Bear standard of defense is defined by the terror noted in the Qb's eyes, the errant passes, interception, fumbles and turnovers created. The bears defense should cause so much havoc that opposing offenses are penalized more offensively for false start and holding because they are so desperate to stop the onslaught attacking on every play endlessly and painfully.
Love the Bears defense, we can get better.